wil6210: set ip_summed to CHECKSUM_UNNECESSARY if no error found

In EDMA, checksum was not set to CHECKSUM_UNNECESSARY when no
errors were reported from HW, causing checksum to be calculated
by network stack.

Change-Id: I4847ddbf1dcb5151fbbd4f12ce467096e839a8c5
Signed-off-by: Alexei Avshalom Lazar <ailizaro@codeaurora.org>